Curved plywood structure



DBC. 19,' 1944. A, DE VR|E5 2,365,3347

y ouRvEDYPLYwoon STRUCTURE Filedseptjza, 1945 Patented Dec. 19, 1944 iJNlTEDV STATES PATENT OFFICE CURVED PLYzsl4STRUCTURE I D Nicholas A. de Vries, Brookeld Center, Conn.

Application september 2s, 194s, serial No. 504,094

` 1 claim. .(ol. 144-309) This invention is directed to an improvement in curved plywood structures, and has for one of its objects to provide a plywood construction which may take a great variety of curved shapes, is exceedingly strong and rigid, and wherein inner stresses tending to'cause the plywood to return to its original shape are reduced to the very minimum.

A further object of the invention is to provide a curved plywood construction wherein it is unnecessary to employ wet steam or other moisture means when conforming the plywood to shape and wherein instead of the necessity of employing the more or less expensive cauls commonly employed in this industry the most involved curves of one kind and another are desired, to

place the plywood in steam presses and to subject the plywood to tremendous pressures While moist. The hope is that the plywood will take the shape of the dies of the press and retain that shape indefinitely. However, this has been found difficult of attainment and the equipment necessary is bulky and expensive. Under such conditions internal stresses are set up in the material always tending to return the work to its original shape.

It is my object to-'eliminate this difficulty which is a real drawback in this industry, and to produce a construction wherein the expensive equipment heretofore thought necessary together with the time and skilled labor that goes with it may be eliminated, while at the same time I provide a construction in which internal stresses are not set up to a detrimental extent, so that notl only may I construct curves which are inexpensive to produce, relatively speaking, but I have the assurance that the workpiece will retain its shape indenitely.

AThese features of my invention are of very material value also in cases where, for example, it is required to produce a. great number of pieces of identical shapes and dimensions; for example, in chair seats wherev a great number of seats are to be produced, and where they must all be alike in order that assembly with the other parts of the chair may be accomplished with the maximum of accuracy and in the minimum of. time. It is a simple matter in the practice of my invention to lay out the desired shape on the drawing board, and with simple hand equipment bend the plywood to this shape, with the assurance that it will retain this shape indefinitely.

Another advantage inherent in my invention is the fact that I employ plywood of regular construction -and with the very minimum of expense convert it to my use, as distinguished from present practice where the separate layers com'- prising the plywood structure are glued while being bent to shape.

l Broadly speaking, my invention provides a plywood construction wherein two plywood strips kerfed on one face are glued together while bent to the desired shape with their kerfed faces juxtaposed.

I am aware, of course, that it is old to kerf a piece. of lumber transversely of the grain to facilitate bending of the same. It is my desire, however, to go beyond this. I wish to provide a construction which is in nished condition so far as its outer surfaces are concerned, all in the one operation, and a construction in which thick pieces readily may be bent to shape with:v

the assurance that when finished they will remain in that conditionindenitely.

In the accompanying drawing I have shown a chair seat by way of illustration of the invention:

Fig. 1 is a plan view of the seat; J

Fig. 2 is an end view of the seat; and

Fig. 3 is a section on the line 3 3 of Fig. 2.

Referring to the drawing in detail: 2 designates a plywood strip and l another smilar'plywood strip which are to comprise .the seat.

Thel plywood strip 2 comprises outer veneer The grain of the core I4 extends in the same di.

rection as that of the outer veneer layer 6, that of intermediate layer I0 is transverse of that of the core piece while the grain of inner layer i2 is transverse of I 0. In other words, the grain of any layer extends transversely of the immediately adjacent layer or layers.

The plywood strip 4 is of similar construction, being composed of outer veneer layer 24, inner veneer layer I 8, core piece 20 and intermediate veneer layers I8 and 22.

In the seat illustrated in the drawing I have elected to show a very pronounced curve at the rear portion of the seat, the axis of this curve extending generally parallel to the grain. of veneer layer S. This curve gradually fades out until at the front of the seat a substantiallyat surface is Provided. The curved area has been designated 26 while the flat area is designated 28. It, is to be understood that such showing is purely illustrative, inasmuch as the construction I employ is adapted for the making of any curved shape. illustrate the possibilities of my invention, as such a shape is very diicult to obtain with usual constructions and very difficult to retain indefinitely.

The inner face of the plywood strip 2 is kerfed lengthwise, as shown at 30, that is to say, the kerfs extend in the same general direction as the grain of outer veneer 6 substantially parallel to the axis of the curve about which the wood is bent. 'I'he kerfs, it is to be noted, are not only cut through the inner and intermediate veneers i2 and lil but completely through the core piece I4, as well, and because of the shape to be given the upper surface of the seat the kerfs are outwardly inclined or fanned with respect to the center line of the seat as illustrated in Fig. l. It is to be noted also that the kerfs terminate some distance short of the front edge of the seat.

The plywood strip 4 is kerfed similarly to the kerng of strip 2, these kerfs, designated 32, being cut through the inner and intermediate veneers I6, I8 and through the core piece 20.

After the plywood strips have been kerfed as described they are placed with their kerfed faces in juxtaposition, a suitable glue having first been applied to these faces and then bent cold to the shape desired, and held in this shape until the glue has set up.

With the instant construction where I desire a shape such as I have illustrated, it is quite unnecessary to provide male and female cauls which are large enough .to accommodate the entire seat. It is suiilcient if the curls extend from the front edge of the seat rearwardly of the seat five or six inches, and when but a slight pressure is applied to the cauls the assembly will take the form described. I mention this in passing as a matter of interest to the industry, and not in a limiting sense at all so far as my invention is concerned. The reason for the assembly taking the shape mentioned is because of the kerfs, the direction I selected the shape shown merely to.

in which they extend, their termination short of the front edge of the seat, and the fact that pressure is applied by the cauls to only a relatively small area at and adjacent the rear edge of the seat.

It `will now be apparent that the primary feature of this invention resides in the fact that I employ two plywood strips having their adjacent faces kerfed and glued to eachother, such a construction permitting me to bend the wood into any desired shape, all bending taking place, of course, before the glue bonding the two strips sets, with the assurance that after the` glue has set up the assembly will retain this shape, this feature being of very material advantage where manufacture is on a commercial scale, and where.

as is in the case in the furniture industry. for A example, hundreds and thousands of duplicate parts are turned out.

As mentioned above, I have found that my improved construction is of advantage in many directions as compared with existing structures and present day methods of manufacture. For example, all heating is dispensed with, inasmuch as but slight pressure is required to bend the Wood to a desired curve, whether a simple or a compound curve; by the saine token only very slight internal stresses are set up, so that' the tendency of the wood to break the glue bond and return to its original shape is negligible; this same feature. lack of any tendency of the wood to straighten out, facilitates manufacture of identical pieces in large quantities. It will be appreciated that the number of plies employed in the plywood strips in practicing my invention may be varied from that described and that the direction of the grain of the wood in layers composing the structure may be varied, all within the purview of my invention.

What I claim is:

'I'he method of forming curved structures from a pair of plywood strips each of which comprises an inner and an outer layer and an intermediate core piece adhesively secured into a unit, said method comprising kerilng one face, including the core piece, of each of said plywood strips, and 

